Roberto Mancini, Manchester City's manager, says he cannot understand why the club allowed Daniel Sturridge to join their rivals Chelsea, and he is worried that City will pay when the teams meet in a vital Premier League game at Stamford Bridge tomorrow night. The England forward was allowed to leave two years ago, while Mark Hughes was City's manager, after he demanded wages reported to be £55,000 a week. A tribunal fixed the transfer fee at£3.5 million, which has subsequently risen to £6.5m, including £1m when he won a first full cap last month.

After scoring eight goals in 12 games for Bolton on loan last season, Sturridge has been in outstanding form and displaced Nicolas Anelka, who will be allowed to leave in January.

Mancini said: "I asked him last year, 'Why did you leave Manchester City?' and he said he doesn't know. It was strange, because someone let him out of the club. For sure he was one of the best young players that was here. Sometimes it's difficult with a young player,but it was not difficult to see if Sturridge was a good player. If he was here today he'd be in the first team."

Chelsea go into the game 10 points behind City but their manager, Andre Villas-Boas, has said they will still be in contention for the title if they win.

Yesterday, second-placed Manchester United reduced City's lead to two points by beating Wolverhampton Wanderers 4-1, with two goals each from Wayne Rooney and Nani. Third-placed Tottenham, five points behind United, travel to Stoke today.

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